Human pathogenic bacterium induces actin phosphorylation to selectively regulate

描述(由申请人提供)：许多细菌病原体在进入/内化过程中或在细胞间传播时利用宿主肌动蛋白细胞骨架。病原菌在节肢动物载体中使用肌动蛋白细胞骨架还没有被探索过。本研究以人粒细胞无形体病原体--肩部硬蜱和无形体吞噬细胞为感染模型，首次证明了专性细胞内细菌如何利用肌动蛋白细胞骨架来控制节肢动物基因的转录，从而达到自身的目的。我的初步结果表明，吞噬弧菌可以诱导壁虱肌动蛋白的磷酸化，进而改变单体/丝状肌动蛋白的比例。我还发现，吞噬革兰氏菌诱导的肌动蛋白磷酸化依赖于硬蜱PAK1-PI3K信号。吞噬细胞素诱导的肌动蛋白磷酸化导致与RNA聚合酶II(RNAPII)相关的核G-肌动蛋白和磷酸化肌动蛋白增加。在细胞核中诱导肌动蛋白的磷酸化增强了TATA盒结合蛋白与RNAPII的结合，并导致了对吞噬阿糖胞菌生存至关重要的基因salp16的选择性调控。本项目旨在探讨salp16启动子的选择性调控在吞噬弧菌感染中的作用机制。建议进行更多的研究，以确定是否有任何细菌成分(S)或其他硬体动物转录激活因子(S)参与了这一特定的基因调控。总之，这项研究可能为肌动蛋白磷酸化在宿主-病原体相互作用中的新作用提供证据，并提出新的策略来干扰这种专性细胞内病原体的生命周期，也许还有其他医学上重要的立克次体相关微生物。 与公共卫生相关：在美国，肩部硬蜱传播几种人类病原体，包括人类无浆体病原体吞噬细胞素。这种细菌在其载体宿主中生存所使用的分子机制目前尚不清楚。该项目提案为肌动蛋白在宿主-病原体相互作用中的新作用提供了证据，并提出了新的策略来干扰这种专性细胞内病原体的生命周期，也许还干扰了其他节肢动物传播的具有重要医学意义的微生物。

DESCRIPTION (provided by applicant): Many bacterial pathogens exploit host actin cytoskeleton either during entry/internalization or spread from cell to cell. Pathogen use of the actin cytoskeleton in arthropod vectors has not yet been explored. Using Ixodes scapularis ticks and Anaplasma phagocytophilum (the agent of human granulocytic anaplasmosis) as an infection model, I provide evidence for the first time to show how an obligate intracellular bacterium can exploit the actin cytoskeleton to control arthropod gene transcription for its own benefit. My preliminary results show that A. phagocytophilum induces the phosphorylation of tick actin and subsequently alters the ratio of monomeric/filamentous (G/F)-actin. I also show that A. phagocytophilum-induced actin phosphorylation is dependent on Ixodes PAK1-PI3kinase signaling. A. phagocytophilum-induced actin phosphorylation resulted in increased nuclear G-actin and phosphorylated actin that associated with RNA Polymerase II (RNAPII). Induced actin phosphorylation in the nucleus enhanced binding of TATA-box-binding-protein to RNAPII and caused the selective regulation of salp16, a gene crucial for A. phagocytophilum survival. This project proposal explores to identify the mechanism by which selective regulation of salp16 promoter is mediated upon A. phagocytophilum infection. Additional studies are proposed to identify whether any of the bacterial component(s) or other Ixodes transcriptional activator(s) are involved in this specific gene regulation. Collectively, this study may provide evidence for a novel role of actin phosphorylation during host- pathogen interaction and suggest new strategies to interfere with the life cycle of this obligate intracellular pathogen, and perhaps other Rickettsia-related microbes of medical importance. PUBLIC HEALTH RELEVANCE: In United States, Ixodes scapularis ticks transmit several human pathogens including A. phagocytophilum, the agent of human anaplasmosis. The molecular mechanisms that this bacterium uses to survive in its vector host are currently not understood. This project proposal provides evidence for a novel role of actin during host-pathogen interaction and suggests new strategies to interfere with the life cycle of this obligate intracellular pathogen, and perhaps other arthropod-borne microbes of medical importance.